1. Field of the Invention
The invention relates to a driving circuit of a display; in particular, to a level shifter of the driving circuit applied in the display and operating method thereof.
2. Description of the Related Art
In a conventional driving circuit of a display, when a conventional level shifter converts a signal with low voltage level into the signal with high voltage level in multi-power domain, the conventional level shifter uses many stages of level shifting unit to perform signal voltage level conversions in order, so that the conversion voltage range in every signal voltage level conversion will not exceed the withstand voltages of the MOSFETs in the level shifter to avoid the leakage loss of the driving circuit and extend the life of the display.
For example, as shown in FIG. 1, the conventional level shifter 1 includes five stages of level shifting unit 11˜15, if input voltages of the input terminals IN and INB of the conventional level shifter 1 are 0˜1.5 volts, the input voltages will be converted into output voltage signals OUTP and OUTB with voltages of 6˜12 volts by the five stages of level shifting unit 11˜15 in order, and then outputted by output terminals of the level shifter 1.
However, since 26 MOSFETs (e.g., M1˜M26 in FIG. 1) are used in the conventional level shifter 1 and two additional voltage sources are necessary in the conventional level shifter 1 to provide two middle voltages VCL1 and VCL2 in the signal voltage level conversions, the cost of the conventional level shifter 1 becomes high and the circuit structure of the conventional level shifter 1 becomes very complicated. In addition, since the entire signal voltage level conversion process are performed in four stages in order, it is so time-consuming that the efficiency of the conventional level shifter 1 performing signal voltage level conversions in multi-power domain also becomes poor.